MAKE by @levelsio – Will get you into the right mindset of just going out there and actually doing stuff, rather than just thinkign about it. Since most business skills are learned through trial and error that's a good mentality to get. https://makebook.io

Indie Hackers interviews by @csallen – Both the podcast and the text interviews are a great way to get practical suggestions on how to build an online business. It will also help you get motivated to focus on the business part. https://www.indiehackers.com

MicroConf by Rob Walling and Mike Taber – Conference for bootstrappers. Both the speakers and attendees are great people to be around and learn from. If you go to one event a year, this should be it. They have events in Europe and the U.S. – http://www.microconf.com

There's also FemtoConf in Germany which feels like a mini-MicroConf to me. I haven't attended yet, but if you have a smaller budget and still want to meet similar minded people this might be a good alternative. – http://femtoconf.com/

Apart from that I'd recommend spending time with business savvy people so you can both learn practical tips and mirror their mindset.

All of the material that's come out of MicroConf. They publish all past talks for free and anyone who makes summary books/resources (there are many) is forced to publish them for free as per the conference license agreement.

Annother good start is listening to the podcast odf Sean Mc Cabe: www.seanwes.com
And maybe reading hit book Overlap Technique, where he helps you how you can start a business while still working a dayjob. So overlapping. And eventually move to having your own business.